TR2/3/3A Another brake bleed question.......

[karls59tr]

I successfully bled the brakes(bled the MC separately) and the pedal is where it is supposed to be. With the brakes off why would the disk on the drivers side spin so much more freely than the pass side disk? It's not locked up or anything just somewhat harder to spin. The brake pads are brand new and you can hear the pads rubbing the disk but they have not been broken in yet. Is this something that will sort itself out once the pads are broken in or should I try to re bleed the caliper on the side that has more drag?

 

[charleyf]

The front disc brake system is self adjusting. Therefore it should work itself out.
Charley

 

[RGK]

Front wheel bearings adjusted correctly?

 

[Hamish Racing]

Both Charley and RGK have very wise observations in my mind.

if there is no real drag and you can turn the hub by hand ( without the added leverage of the wheel) it shouldn’t be too tight. ( check the passenger side isn’t too loose) I would be tempted to go for a run and follow the pad manufacturer break in method and see how things settle.
They are not bicycle wheels that spin for ever.

 

[CJD]

I would run it. If it still bothers you, though, you can check the pass side rotor runout. If the runout is within .005"...then it's just a matter of new parts bedding in.

 

[karls59tr]

Front wheel bearings adjusted correctly?

I will check the whee bearing free play

 

[karls59tr]

I would run it. If it still bothers you, though, you can check the pass side rotor runout. If the runout is within .005"...then it's just a matter of new parts bedding in.

The rotors are new. I'll give it a run and see if the new pads bed in. Is there a standard "bed in" procedure to ensure the pads mate up properly to the rotor?

 

[charleyf]

I recall from one of your recent posts that you were concerned about centering the front brakes on the disc. You were going to leave it close , as I recall. If you left it close then what did you expect to get until the pads wear in?
It sounds to me like you are looking to hard for problems. Relax and enjoy your TR.
Charley

 

[karls59tr]

.IMy concern relates to the fact that the front drivers side wheel on my TR3 once locked up when I was going 70 mph. I fought the car over to the side of the road. There was a grease fire near both calipers that I put out with road gravel. After the tow truck brought the car home I took a look at the front wheel that was canted over about 15 degrees. The disc was heat damaged and scorched ,the caliper was damaged,the stub axle was ruined. i don't know why this happened and I'm being extra cautious with the new brake setup.I don't need the kind of adrenaline rush this incident caused.

 

[61forfun]

rebuild the calipers. Sounds like you have a sticky one. How old are the flexible brake lines?

 

[charleyf]

rebuild the calipers. Sounds like you have a sticky one. How old are the flexible brake lines?

That sounds a lot like a bearing problem. Hence the 15 degree angle.
Charley

 

[CJD]

New rotors do not mean they will not have runout. You could have a bent hub or damage to the hub face that will cause the runout.

 

[karls59tr]

rebuild the calipers. Sounds like you have a sticky one. How old are the flexible brake lines?

The calipers have been rebuilt. The old caliper pistons did not look particularly bad. Not rusty and popped out easily enough. The brake lines on the car were the stainless steel ones when I had the accident.

 

[61forfun]

The calipers have been rebuilt. The old caliper pistons did not look particularly bad. Not rusty and popped out easily enough. The brake lines on the car were the stainless steel ones when I had the accident.

Well sir. How firm is the pedal? If the pedal stops adjustments at the push rod ( going into the master cylinder) are too tight, the piston will not go back far enough inside the master cylinder to allow the fluid to return into the master cylinder reservoir, thereby not allowing your calipers to be relieved of fluid, causing them to stay on. Had that issue on my Sprite. Two 7/16” wrenches later the adjustment fixed the issue.

 

[bobhustead]

Karl
If you go to a NASCAR race and watch the front wheels, the rotors are literally cherry red for 3 or 4 hours at a time. As Charly said, hot rotors were not the cause of your hub and stub axle failure. If push rod adjustment were keeping pressure on a caliper, it would be keeping pressure on both calipers. Hydraulic pressure at any point in a single system is the same as at any other point. A locked up piston is possible, but the first suspects are new pads being too thick or a rotor with runout.
Bob

 

[karls59tr]

Well sir. How firm is the pedal? If the pedal stops adjustments at the push rod ( going into the master cylinder) are too tight, the piston will not go back far enough inside the master cylinder to allow the fluid to return into the master cylinder reservoir, thereby not allowing your calipers to be relieved of fluid, causing them to stay on. Had that issue on my Sprite. Two 7/16” wrenches later the adjustment fixed the issue.

I think that may have been what happened. At some point before the accident I had replaced the the TR3 brake light switch, which is an inline unit under the car, with a TR4a switch( a small box like unit with a button) that I mounted in front of MC box surround. The threaded part of the switch and the stop light button may have protruded into the area of the brake MC rod just enough to prevent the rod from returning as you describe! The TR3 setup had a stop bolt on the MC box surround to limit the travel of the rod. Triumph did away with the stop bolts later on in production and what you describe is probably why? Now that I have gone back to the inline switch and use a stop bolt I can get the correct pedal height, which lines up with the clutch pedal height, I get good brakes that start to apply after a couple inches of depression. But if I remove the stop bolt the pedal is way too low and much more distance of depression is required?

 

[karls59tr]

Karl
If you go to a NASCAR race and watch the front wheels, the rotors are literally cherry red for 3 or 4 hours at a time. As Charly said, hot rotors were not the cause of your hub and stub axle failure. If push rod adjustment were keeping pressure on a caliper, it would be keeping pressure on both calipers. Hydraulic pressure at any point in a single system is the same as at any other point. A locked up piston is possible, but the first suspects are new pads being too thick or a rotor with runout.
Bob

Bob I see your point. I think both calipers actually did lock up as the grease fires were on both sides but the caliper on the drivers side failed first. The other thing is I had been mucking about with the front wheel bearings trying to get the right endplay and I may have screwed that up so the wheel was actually too loose and contributed to the failure. See my post about how I mounted the TR4A stop switch which may have contributed to the lock up. Karl

 

[karls59tr]

Karl
If you go to a NASCAR race and watch the front wheels, the rotors are literally cherry red for 3 or 4 hours at a time. As Charly said, hot rotors were not the cause of your hub and stub axle failure. If push rod adjustment were keeping pressure on a caliper, it would be keeping pressure on both calipers. Hydraulic pressure at any point in a single system is the same as at any other point. A locked up piston is possible, but the first suspects are new pads being too thick or a rotor with runout.
Bob

Bob See my post about the brake MC rod length.